Browsing by Author "Acres, RG"

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    Adsorption structure of adenine on cerium oxide
    (Elsevier, 2020-11) Bercha, S; Bhasker-Ranganath, S; Zheng, X; Beranová, K; Vorokhta, M; Acres, RG; Skála, T; Matolín, V; Prince, KC; Xu, Y; Tsud, N
    The adsorption of adenine on the CeO2(1 1 1)/Cu(1 1 1) surface in vacuum was studied by photoelectron spectroscopy, resonant photoelectron spectroscopy and near-edge X-ray absorption fine structure spectroscopy, and the present work describes in detail the bonding of the molecule to the ordered stoichiometric cerium dioxide film. The experimental findings were supported by density functional theory (DFT + U) analysis of different adsorption geometries of adenine on CeO2(1 1 1). The phase with adenine lying flat on the surface dominates on CeO2(1 1 1) up to 0.1 monolayer (ML) of adenine coverage. The mobility of single molecules was apparently sufficiently high to allow diffusion and formation of chain structures, which were observed to be stable in the temperature range from 25 to 250 °C. Beyond 0.1 ML, adenine molecules adsorb predominantly in an upright orientation. This phase, stable up to 120 °C, is according to theory stabilised via N3/Ce4+ and N9H/O2–. It was further complemented by experimental findings demonstrating free N10H2 groups in adsorbed molecules. Thus, the saturation coverage of adenine on CeO2(1 1 1), 0.23 ML, is most likely characterised by a combination of parallel and upright bound molecules. © 2020 Elsevier B.V. All rights reserved.
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    ANSTO and the Australian Synchrotron: product development, process improvement and problem solving for materials science and industry
    (Materials Australia and the Australian Ceramic Society, 2018-11-27) Acres, RG
    ANSTO operates some of Australia’s world class national research infrastructure. Facilities like the Australian Synchrotron and the Australian Centre for Neutron Scattering provide cutting edge tools to academic and industry researchers, empowering them to problem solve and innovate in a wide range of sectors, including materials science, additive manufacturing, alloys, ceramics and polymers. As well as servicing the traditional academic user base, ANSTO has an Industry Engagement team focused on supporting commercial customers to utilise the synchrotron’s capabilities. However, going beyond the academic user base presents some challenges as well as opportunities. This presentation will: * Discuss how to raise awareness and understanding of technical capabilities to potential commercial clients * Share ways to inspire businesses to explore applications and capitalise on the opportunities arising from our world class infrastructure * Showcase existing case studies, demonstrating successful connections between science and industry Examples of case studies with industry partners will be presented that highlight the capabilities and advantages of ANSTO to commercial and academic users. Lessons learned will be shared as well as a practical approach to achieving “buy in” from key decision makers to achieve mutually beneficial outcomes.
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    Combined SRCT & FXCT – the next steps
    (IOP Publishing, 2016-03-22) Hall, CJ; Acres, RG; Winnett, A; Wang, F
    One of the goals in developing synchrotron radiation x-ray computed tomography (SRCT) for biomedical specimens, is allowing particular tissues and cell types to be marked in the images. This is equivalent to the staining in histology, which enables researchers to visualise and measure tissue structure and biochemical processes within the specimen. Some progress in this direction for SRCT is being made, using a variety of contrast agents that alter the natural x-ray attenuation of the marked tissue [1]. However there are limits to the usefulness of these attenuation altering techniques. Often high concentrations of potentially disruptive chemicals are required with reduced compatibility for in-vivo studies. Another image highlighting technique which might prove more sensitive is x-ray fluorescence imaging. In this case usually endogenous elemental markers are visualised. We would like to develop a lower resolution, but wider field of view means of three-dimensional (3-D) fluorescence imaging compatible with SRCT. We have previously proposed a technique in which x-ray fluorescence CT (FXCT) and SRCT data can be collected simultaneously [2]. This work resulted in proof of concept modelling, and a simple experiment test system. We show data here which demonstrate a two-dimensional (2-D) reconstruction of an iodine fluorescence map from a phantom. Measurements were performed with a fixed beam modulating mask using the Imaging and Medical beam line (IMBL) at the Australian Synchrotron. Fluorescence data was obtained during a CT scan using a single point detector, while transmission data was simultaneously collected using an area detector. A maximum likelihood expectation maximisation (MLEM) iterative algorithm was used to reconstruct the fluorescence map. We report on technique development and now believe compressive sensing (CS) imaging techniques suit SRCT and may overcome the issues encountered so far in combining SRCT and FXCT. © 2016 IOP Publishing Ltd and Sissa Medialab srl.
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    Electronic structure and intramolecular interactions in three methoxyphenol isomers
    (AIP Publishing, 2018-10-07) Islam, SMA; Ganesan, A; Auchettl, R; Plekan, O; Acres, RG; Wang, F; Prince, KC
    Electronic structures and intramolecular interactions of three methoxyphenol positional isomers and their rotamers have been studied using core X-ray photoelectron spectroscopy and quantum mechanical calculations. The structural calculations are benchmarked against published calculations of enthalpy of formation and rotational constants, and published experimental data. The good agreement obtained confirms the accuracy of the results. A single rotamer of each isomer was then selected and the C 1s photoelectron spectra calculated and compared with experiment. Good agreement is obtained, and the calculations were extended to investigate the effects of conformation. For 3-methoxyphenol, the difference in the C 1s binding energy of the conformers is small, <0.15 eV. For 2-methoxyphenol, whose ground state includes an OH⋯OCH3 hydrogen bond, the higher energy rotamers show the largest shifts for the methyl carbon atom, whereas the ring carbon bonded to OH hardly shifts The theoretical differences in core level energies of the two rotamers of 4-MP are still smaller, <0.05 eV. By comparing calculations neglecting or including final state relaxation upon ionization, the relaxation energy of the phenyl carbons in all isomers is found to be ∼0.5 eV, while that of the methyl groups is ∼1.3 eV. © 2018 Author(s).
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    Microtomography applications at the Imaging and Medical Beamline of the Australioan Synchrotron (sic)
    (Australian Microscopy and Microanalysis Society, 2016-02-04) Maksimenko, A; Acres, RG; Hall, CJ; Häusermann, D; Stevenson, AW; Livingston, J; Pearson, J
    The Imaging and Medical Beamline (IMBL) of the Australian Synchrotron (AS) is now becoming one of the most advanced instruments of this type in the world. It is designed to provide a wide variety of imaging techniques including but not limited to the in-line and analyzed phase contrasts, monochromatic and pink beam imaging. Three beamline’s enclosures at various distances, when combined with the 25kW superconducting multipole wiggler and double Laue bent monochromator provide the end user a good choice of beam characteristics ranging from the hi-flux for high resolution and size up to huge 48x5cm beam at 134m from the source with the allowed energy range 17-120kEv. The wide range of the area detectors allows the computed tomography (CT) and tomosynthesis methods to be applied to almost any known X-ray imaging modality. The beamline’s data acquisition system is directly linked to the high performance computing facilities tuned for the on-the-fly real-time reconstruction and 3D rendering. Deep integration of the acquisition, reconstruction and rendering facilities allows one to think of the their combination as of a single system with modular architecture. The system is designed for the fully automated experiments with minimal user interaction. This report summarizes implemented, designed and planned features of the beamline as applied to the microtomography experiments. Some latest outcomes of the CT system are presented with the samples coming of different fields of science: Biology, Geology, Paleontology, Medicine and others.